TESTING AND BALANCING
WHY COMMISSION
MECHANICAL SYSTEMS?
Excerpted from ENVIRONMENTALLY SPEAKING, V1 No.4
T
hroughout the 1990's and into
the turn of the century, testing,
adjusting, balancing (TAB) will
assume a role as the most critical
phase of mechanical systems commissioning. Qualified service firms
throughout the country will be called
upon to fine-tune a variety of complex
systems and to resolve an ever increasing number of environmental problems.
"neutral." In a situation where more
air is brought in than is being exhausted, the building is said to be
"positive." Conversely, a building
which brings in less air than it exhausts is said to be "'negative."
This relationship of air inside a
building to air outside a building is
the differential pressure. Since air acts
like a fluid, it will flow from the positive area to the negative area or from
higher pressure to lower pressure.
Regulating air balance, whether its
Comparing inside to outside or comparing one zone to another is extremely important. Indoor Air Quality
(IAQ), occupant comfort, system efficiency, and correct air flow are greatly
affected and enhanced by proper air
balance.
TAB is integral to an effective
HVAC system, but has not received
due respect until recently. Lately,
TAB workmanship has improved,
reports are easier to understand, and
better instrumentation has been introduced.
Certification agencies such as National Environmental Balancing Bureau (NEBB) or Associated Air Balance Council (AABC) have
experienced unprecedented growth.
The majority of consultant's specifications in the future will demand
"certified" system adjustments as
part of the system commissioning
process.
In modem HVAC systems, provisions are made for equipment to recirculate conditioned air, exhaust air,
and to bring in make-up (outside)
air.
The balance, which is struck between the volume of exhaust and
make-up air, is called air balance. If
the amount of air brought into the
building is equal to the amount exhausted, the building is said to be
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MORE ON
COMMISSIONING
W
henever air is exhausted
from a building, the building becomes negative. As a
result, outside air will enter the building in some manner to "make-up" or
balance the exhausted air. This makeup air can either be managed or mismanaged.
One of two situations arise if makeup air is mismanaged. The building
will become too positive or too negative. When a building is too positive
or has too much outside air, it can use
excessive energy to condition this air.
heating coils, dampers and equipment
o Identify unusual noises within the
system. Verify control system operating properly. Check responses of any
computerized energy management
systems.
needs will find water-side balancing
to be as detailed and important as the
air distribution process.
The equipment and reports of the
"certified" TAB firm allow the Facility
Manager to feel comfortable that all
It's worth noting that the above check- instrumentation utilized I for mealist deals with air distribution systems surements is calibrated accurately and
only. Waterside systems also take a that personnel performing the work
meticulous analysis of water flow are trained and continuously eduthrough hydronic heating and cooling cated. These latter two items are a fundamental criteria for achieving and resystems.
maining certified by either NEBB or
Customers with water balance AABC.
The second and more common result of mismanaging or ignoring
make-up air is an unwanted negative
building. A negative building will
draw air in from anywhere it can. This
air might come from undesirable
sources such as trash bins, grease
traps, truck docks, open doors, windows, cracks, etc.
Every bit of unfiltered air or unconditioned air will affect an HVAC systems ability to maintain the desired
environment. Buildings with this
problem are dirtier, draftier, insect
laden, and seldom comfortable.
The following check list gives the
Facility Manager an opportunity to
know what an air balance team will
need in order to do their job. Obtain
as-built drawings. Perform physical
survey to compare actual conditions
against as-built drawings.
o Measure cubic feet per minute
(CFM) of air being supplied to each
diffuser
o Measure discharge/return air volume and temperatures at unit. Measure revolutions per minute of blowers
o Measure voltage and current draw
of motors
o Check condition of all cooling and
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MANAGING OUTSIDE
AIR FOR BETTER IAQ
T
o maintain a comfortable and
healthy indoor environment,
sufficient outside air (OSA)
must be introduced to the occupied
building space. The Energy crisis of
the 1970's caused the government to
mandate that small (inadequate)
amounts of ventilation air be used in
the design of HVAC systems. The result was the construction of many
buildings with problems ranging
from slight discomfort of occupants to
"sick building syndrome."
Most current codes are based on
ASHRAE Standard 62-1989 and require OSA quantities based on the
number of occupants and building usage. Requirements range from 15 to 25
cubic feet per minute (CFM) for normal working areas.
Normally, ten feet of separation from
a plumbing or appliance vent outlet is
required unless the vent is three feet
or more above the air inlet.
The most effective means of assuring adequate OSA is through direct
connection to the HVAC unit or supply fan. Wall louvers, soffit grilles, or
intake vents above the roof are commonly utilized for air intake.
Accurate air balance and a good control system are essential elements for
assuring that adequate OSA arrives in
the spaces. For small systems (usually
up to 2,000 CFM of total circulated air),
manual OSA and return air dampers
are set for desired OSA intake.
Larger systems require automatic
variable air quantities (such as VAV)
need special attention to insure conformance to OSA standards.
Demand ventilation control is a
cost-effective means to lessen energy
consumption and maintain good indoor air conditions. A CO2 sensor or
air quality sensor may be used to determine OSA quantities. This sensor
signals a control device, and causes
automatic damper adjustments to
maintain adequate amounts of OSA.
Occupant complaints, illness, or
discomfort due to improper or inadequate air circulation can be costly due
to loss of productivity or in extreme
cases, litigation. The proper design
and operation of a building's HVAC
system gives good command of temperature, humidity, air cleanliness
and air motion, minimizing occupant
complaints and maximizing comfort.
Effective control of OSA is a fundamental component of this process.
You may need to consider having
your systems balanced when one or
more of the following problems exist::
• The space configuration has
changed since the last air balance.
• Maintenance personnel must continuously readjust control settings.
• Indoor air quality (IAQ) is a concern (ASHRAE 62-1989 Compliance)
• Odors are present inside the building or hot and cold spots exist.
• The building is drafty or stuffy —
doors stay open or slam-closed.
OSA intake should be located with
care so as not to take air from garages,
crawl spaces, loading docks, or other
hazardous or unsanitary locations.
damper systems. Indoor fans should
run continuously during occupied
hours rather than only when heating
or cooling is required. Systems with
Considering the costs associated
with a nonproductive workplace, it is
to the owner's advantage to have a
TAB team make sure these problems
are addressed. As we move closer to
the turn of the century, testing, adjusting, and balance will become a core
competency that every building
owner will demand from his facility
management company or mechanical
service and maintenance provider.
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HOW TO RESPOND TO
AN HVAC TEMPERATURE
COMPLAINT
I
n
today's
sophisticated
economy, customer expectations
have grown to require quick professional response to service needs.
Building Owners and Management
Association (BOMA) has determined
that the most commonly stated reason
for tenants not renewing their lease is
due to faulty heating, ventilation and
cooling systems or poor service.
Therefore, building owners and managers should form an alliance with a
quality HVAC service company, so
that tenant satisfaction can be maximized.
The most effective alliance is one
that is formed when the building
manager and service company take
equal responsibility for serving the
customer. Too often the responsibility
is left with the service company and
the service technician in the field.
Imagine a conscientious service technician getting to a job site within one
hour after he received the call only to
find an angry tenant who informs
them that the call was placed numerous hours ago or maybe even the previous day.
Whether it was the building management office who delayed calling
the service company or a busy technician work load, the service technician
is already at a disadvantage.
Arriving in mid-afternoon after a
building has warmed up to resolve the
complaint which originally occurred
when the building was too cold in the
morning, places a service technician at
a distinct disadvantage. A service
technician needs accurate, specific information prior to arriving at the
building if he or she is going to build a
good business relationship with the
building tenants and property management company.
Prior to the technician's arrival, the
service company should telephone the
person who originated the call and inform them that the, technician has
been dispatched and the expected
time of arrival.
Before the technician leaves the building, they should inform the building
occupant and building manager of the
results of their visit. These individuals must be informed if the job has
been completed, or if not, when they
expect to return to complete the job.
If this communication is consistent,
the building occupant, building manager, and service technician will develop a close working relationship
which will result in happier tenants.
A service call typically originates from
an employee of the tenant. By the time
the call is relayed from tenant management to the building manager and
then sent to the service technician by
the HVAC service company, the original complaint may be distorted and/ or
the actual problem harder to locate.
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